Liquid crystal displays (LCDs) are becoming increasingly prevalent in high-density projection display devices. These conventional high density projection color display devices include a light source which emits white light. Dichroic mirrors separate the white light into its corresponding red, green and blue (RGB) bands of light. These color bands of light are then directed toward a corresponding liquid crystal valve which either permits or prevents the light transmission. The RGB bands of light which are permitted to be transmitted through the light valves are then combined by a prism assembly. A projection lens then magnifies and projects the image onto a projection screen.
A conventional liquid crystal plate comprises lens arrays, a lens for collecting white light from a source and dichroic mirrors for separating the white light into red light, green light and blue light. A polarizing beam splitter (PBS) separates the s-polarized-light components of the red, green and blue range. It allows the separated s-polarized-light components of the light to project on reflex crystal plates and a cross dichroic prism for synthesizing the image lights of p-polarized-light components. The p-polarized-light components are modulated and reflected to be output. A projection lens projects the image light on a screen.
In the current form of the technology, the imager prisms in liquid crystal on silicon (LCoS) light engines are mounted in a precise manner about the prism assembly to aluminum plates that expand or contract with thermal change. The thermal flexing of these plates pushes the sensitive prism alignment out of the focal plane and mis-converges the imager prisms to one another.
The liquid crystal display device described in U.S. Pat. No. 5,537,171, entitled “Liquid Crystal Projection Display” to Ogino et el., is confined to a liquid crystal panel means, a projection lens means and a screen means that enhances relative corner illuminance without reducing light capturing efficiency. However, the display device does not reduce the convergence and focus drift of its prism assembly due to thermal fluxing.
The liquid crystal projector described in U.S. Pat. No. 6,343,864, entitled “Liquid Crystal Projector Equipment” to Tajiri, is confined to mounting polarizing beams splitters (PBS) in the manner where the PBS is mounted about a prism quad assembly to aluminum plates that flux with thermal change. This arrangement produces convergence and focus drift of its prism assembly where there is thermal change.
What is needed is an apparatus that will isolate sensitive optics from the thermal fluxing produced in all the imagers in LCoS light valves.